To evaluate the changes in the microcirculation of the liver, kidney and spleen during acute infection in patients with malaria (cohorts 1 and 3) and other infectious diseases such as acute pyelonephritis at day 0 (within 8 hours of the treatment start), day 2 to 4 and day 28-32, using functional US with continuous infusion of a contrast agent (SonoVue, Bracco, Italy).